python基础--二分查找

# 二分查找

def sort_search(lst,key):
    """
        二分查找
    :param lst: 有序数列
    :param key: 要查找的关键值
    :return: key在数列中的索引
    """
    low, high = 0, len(lst)-1
    while low < high:
        mid = (low + high)//2
        if lst[mid] < key:
            low = mid + 1
        elif lst[mid] > key:
            high = mid - 1
        else:
            return mid
    return None

l = [1, 2, 3, 4, 5, 6, 7, 8, 9]
print('key index:',sort_search(l,80))